Emerald Ash Borer and Urban Trees

EAB-logoWhat’s the big deal about the emerald ash borer? According to the Colorado Tree Coalition, the emerald ash borer (EAB) has killed millions of ash trees since its discovery in 2002 and the number of dead ash is increasing rapidly. Ash species are abundant in planted and natural areas of urban forests, representing 10–40% of the canopy cover in many communities. Ash trees provide substantial economic and ecosystem benefits to taxpayers, ranging from increased property value, to storm water mitigation, to decreased energy demands.

Our fellow researchers at the USDA Northern Research Station say that widespread ash mortality in urban forests and residential landscapes is having devastating economic and environmental impacts. EAB is predicted to cause an unprecedented $10-20 billion in losses to urban forests over the next 10 years.


Damage by building: Photo by Joseph O’Brien, USDA Forest Service, courtesy of Bugwood.org.

Why has this little bug become such a huge problem? In its native range, natural enemies, such as parasitic wasps, are thought to keep populations under control. In North America, this beetle has no natural enemies. Because they are not in their original habitat, invasive species rarely have the checks, such as predators and diseases, that keep them from taking over in their native ecosystems. EAB kills all species of ash trees, often within 2 or 3 years after the trees have been infested. The biggest threat by invasive species to our natural resources is their effect on biodiversity.

The primary regulatory strategy is to create quarantine zones by state and federal agencies to limit the spread of potentially infested materials.

So far, the northern United States have been affected the most by the EAB, as the map shows. Reports are coming in, however, showing that the deadly bug is spreading farther south and east.

For scientists, the details of climate change on the invasion rate of nonnative species are still unclear. It depends on the invasive species’ biology, exactly how the climate changes, and what effect climate change has on a given locale. But one effect the experts seem to agree on is that as habitat suitability moves northward with the warming trend of climate change, invasive species’ ranges will expand there, too. Climate change is a key area of  for the Forest Service and FPL, particularly Supervisory Research Forester Ken Skog and his group, the Economics, Statistics and Life Cycle Analysis Research, which is studying the environmental effects of carbon sequestration, among other things.